مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2056
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas said: Do not criticize the one who fasts when travelling or the one who does not fast, for the Messenger of Allah (ﷺ) fasted whilst travelling and did not fast.
Musnad Ahmad 2057Its isnad is saheeh, Muslim (1113)]